Process of reclaiming rubber



Patented Jan. 24, 1928.

UNITED STATES PATENT OFFICE.

ozone: I. xmmm, or DOUGLAS, ARIZONA. rnoonss or nncmmme nunm Io Drawing.

My invention relates to the artof reclaiming rubber such as is found in old tires, tubes or other manufactured articles composed largely of rubber. It'is general practice in preparing rubber for manufacture into automobile tires or other articles, to incorporate with and into the rubber certain foreign in-' accelerators, etc., (and also cotton in they case of tires). Such augmented rubber is practically valueless for any purpose except that for which it was especially made, and when such manufactured article is worn out, it becomes waste material.

The object of my process is to remove from such worn out articles, or waste rubber material, or rubber scrap,-such an amount of the admixed foreign ingredients as to leave the recovered or reclaimed .rubber sufliciently free of them, and in such condition as regards elasticity, deformability, and other qualities pertaining to rubber, as to permit of its being advantageously and profitably worked up again into new rubber articles, and as to permit of the re-adding of such foreign ingredients as may be necessary to adjust it to its new use.

In its general nature my process is based on certain peculiarities of the solvent action of hot kerosene oil, under controlled and regulated conditions, upon rubber compound, and the present process embodies, in its generic nature, the treatment of the rubber where the presence of some solid fillers in the finished rubber does not constitute an ob'ection, and the procem is carried out as f0 ows, v1z:

-1. The rubber compound is ground by any ad uate grinding method, .to pass a screen 0 16 meshes to the inch, or finer. or

- coarser as desired.

2. The separation of the rubber compound and cotton, when cotton is present, is accomplished by boilin the ground rubber compound, with its ging fragments of cot- Application ma December as, 1926. semi No. 150,525.

ton, in a solution of zinc chloride, acidified with hydrochloric acid, which boiling in such solution disolves the fabric, and also dissolves some of the acid-soluble solid fillers in the rubber compound.

When the cotton has entirely dissolved, the rubber compound is removed from the solution, by draining or filtration, and is then washed free of adhering solution, and

without drying is put through the next operation, as follows:

3. The ground rubber compound thus freed of cotton and some sohd fillers, is placed in a vessel suitable for heating, and covered with kerosene oil, which is kept replenished as the oil soaks into the rubber compound, so that there is alwa s a considerable excess of oil over the ru ber compound. The mixture is heated and maintained at a temperature varying from degrees on the oentrigrade scale to degrees, of the same scale, the tem erature to" be used bein determined by the ardness or softness of t e rubber compound, the harder varieties requiring the higher temperature.

4. The hot kerosene oil dissolves out of the rubber compound free sulphur, much impurities of an organic nature, as vulcanized oils, bitumen products, etc, soaks out some impurities that are not really soluble,

and loosens a certain amount of the solid fillers, which tothat extent are drop ed from the rubber compound, leaving un issolved practically ure vulcanized rubber containing some SOlld fillers. Care is exercised that the temperature and time of heating are so regulated that the vulcanized rubber does not begin to dissolve. During the heating operation the mass is constantly stirred or otherwise agitated to prevent the rubber compound becoming overheated from contact with the hot metal of thevessel. This heating operation is continued until tests or inspection of the rubber show that it has lost all the impurities it can lose under the circumstances, such time usually var from one .half'an hour to one and one-hal hours.

-The vulcanized rubber and kerosene oil are then so arated by draining ed the oil, and the rub er put to soak in some more volatile reagent, as gasoline,carbon bisulphide, carbon tetrachloride, etc., which. will wash out the absorbed kerosene. oil from the rubber, and which can itself be easily dried out of the vulcanized rubber without having permanently injured it in any way. Several changes of these washing rea nts may be used, or anfyrscombination of t em; for instance, the 0 oline, to eliminate the bulk ,of the kerosene, and thefgasoline itself may be subsequently washed out with the more expensive carbon tetrachloride, which is recommended, in

every case where it can be advantageously I. used because of itsnon-inflanimabili When'the rubber is washed free 0 kerosene oil, which uires several hours soaking, it dried, eit er by air-drying, or in a suitable drying arrangement b means of which the volatile reagent may recovered for re-use.- i

From the foregoing description it is thought that m understood by those skilled in the art.

What I claim is: 1. The process of reclaiming rubber from a mass which contains rubber and cotton and other impurities, said process consisting in grinding the mass into particles, boiling the ground mass in a solutlon of zinc chloride acidified with hydroehloric acid until the cotton is dissolved; removing the mass from v the solution and washing it free of adhering.

the washed mass in solution; then plac' I a kerosene oil bath and maintaining the same at a temperature of from 120 C. to 150 C. until the rubber in the mass has lost the maximum 'ble amount of the imurities which it contained, without causing 51sec lution of the rubber, then separating the rubber and kerosene oil andwashing the separated rubber with a suitable washing agent to remove the kerosene, and finally dryin ghthe rubber. 2. e recess of reclaiming rubber from a mass whlch contains rubber and cotton and other impurities, said process consisting in igrindi the mass into particles, boiling the groun mass in a solution of zinc chloride acidified with h drochloric acid until the fabric is dissolv removing the mass from the solution and washin it free of adhering solution; then placing kerosene oil bath and maintaining the same I at a temperature of from 120 C. to 150 C.

t wash may be made with gas-.

invention will be readily e washed mass in a includes t 0 step of treating ber and kerosene oil andwashin the separated rubber with a volatile was agent that is miscible with kerosene oil in order to remove the kerosene oil from the rubber, and finally drying the rubber to free it from the washing agent.

3. The process of reclaiming rubber concotton and other impurities, said process comprising the following steps in the order mentioned, viz: reducing the rubber mass to small particles, separating the rubber compoundand the cotton by boiling the mass in a suitable acidulated solution that will dissolve the cotton and some of the acid-soluble fillers contained in the rubber compound, remo from the solution and washingit free of adhering solution, lacing the rubber com pound in a bath of rosene oil and the same to a temperature of from 120 to 150 C. untilethe maximum amount of zinc chloride acidified with hydrochloric acid to dimolve the cotton, se arating the rubber from the solution after t e cotton has been dissolved, placin the rubber thus freed of cotton in a bath of erosene oil and maintainin the same at a temperature of from 120 to 150 C. until the rubber is freed of free sulphur and impurities of an organic nature and the maximum amount desirable of solid fillers, then separating the rubber from the keromne oil.

5. The rocess of rubber which t rubber to a bath of hot kerosene oil, at a temperature GEORGE J. MILLER.

the rubber compound not to exceed 150 C. for the purpoeea' until the rubber in the mass has lost thefispecified. maximum pomible amountof the impurities 

